The increasing presence of diverse devices interconnected within extensive networks strongly suggests a shift towards a more practical understanding of the Internet of Things (IoT). Numerous researchers and industry experts contend that the forthcoming generation of cellular systems, namely 5G, holds significant promise for advancing IoT deployments. Device-to-Device (D2D) communication appears poised to facilitate the integration of diverse devices and yield substantial benefits. This article comprehensively examines the enhanced functionalities provided by both cellular and non-cellular D2D communications, highlighting their capacity to effectively meet the requirements of IoT within 5G networks. The latest technology solutions, radio technologies enabling and the current D2D communication standard are examined and their advantages and disadvantages are pointed out in the context of multiple IoT usage cases. A full converged 5G IoT ecosystem will be supported with future research instructions.